1. Field of the Invention
The present invention relates to a phantom for standardizing ultrasonograph and a method of obtaining an ultrasonographic image using the phantom, and more particularly, to a phantom for measuring fat content in a target organ as a gray level distribution using an ultrasonographic image and assessing the accuracy of ultrasonograph and a method and apparatus for obtaining a standardized ultrasonographic image using the phantom.
The present invention was supported by the Information Technology (IT) Research & Development (R&D) program of the Ministry of Information and Communication (MIC) [Project management number: 2005-S-069-02, Project title: Development of Wearable System Using Physiological Signal Processing].
2. Description of the Related Art
Ultrasonic waves are sound waves having frequencies above the limits of human audibility. Since ultrasonic waves have short wavelengths and high directivity, ultrasonic waves can be used as a fish finder or a sonar that sends out an acoustic pulse in water and measure distances. Ultrasonic waves can also be used to detect flaws in a solid material, cut or process jewelry or glass, and produce, clean, and sterilize emulsion.
Above all, ultrasonic waves can be used to detect abnormalities on human or animal tissues, and ultrasonic diagnostic systems for such diagnostic purposes are widely used. The ultrasonic diagnostic systems can also detect abnormalities in human or animal bodies in a non-invasive manner. Accordingly, the debate over the use of the ultrasonic diagnostic systems to diagnose many current diseases, e.g., obesity, which is defined as an excessively high amount of body fat and may cause other diseases, is now active. Particularly, the use of the ultrasonic diagnostic systems to measure fat content in a human organ, which is difficult to assess visually, is actively being debated.
Deposits of fat in a human organ may develop various complications, and itself may cause malfunction of the human organ. For example, a fatty liver containing abnormally much fat does not cause pain and does not produce any specific symptoms. Although a slight fatty liver can be found in a healthy person, there is a high probability that fat content in the liver increases abnormally and causes a complication or a hepatocirrhosis. As diet life and obesity are becoming social issues, much attention is drawn to the assessment of fat content in a human liver, and the development of a method of easily measuring fat content in a human organ at low cost.
It is generally known that a fatty liver is closely related to fat content in the liver parenchyma. Although various methods of quantitatively assessing fat content in a target organ have been suggested and carried out, there is a growing need for a method of more easily measuring fat content in a target organ of a human body at a lower cost.
For example, computed tomography (CT) is often used to obtain a cross-sectional image of a human organ, and CT is advantageous in that CT can obtain a high-resolution image and can precisely separate fat from other components in the image without being affected by photographing techniques and conditions. Nevertheless, CT is expensive and dangerous due to radiation exposure.
Also, a biopsy is used to measure fat content in a human organ. The biopsy is a method in which a tissue of an organ, for example, a liver (i.e., a liver biopsy), is removed to analyze the tissue and components of the organ. The liver biopsy can provide very fundamental and reliable results on all kinds of diagnoses and examinations of liver diseases. However, the liver biopsy is complex and invasive to the human body. In addition, the liver biopsy is performed only after there is a sign of disease, and thus, the liver biopsy is not a preventive technique.
Also, ultrasonography is a conventional diagnostic technique based on the cross-sectional image of an organ, e.g., a belly, and ultrasonography is relatively inexpensive and simple to use. In particular, the ultrasonography is safe in that it does not use radioactive rays and is not invasive to the human body. Despite these advantages, the quality of an ultrasonographic image is dependent greatly upon photographing conditions and techniques, and the reflective characteristics and resolution of an object through which ultrasonic waves pass are irregular. For these reasons, there is a high probability that a person diagnosing a disease of a patient may make an arbitrary interpretation on a visual image obtained by ultrasonography, thereby lowering the reliability of the diagnosis of the person.
At present, the clinical determination of a fatty liver using ultrasonography is largely divided into four levels: normal, mild, moderate, and severe. However, an error committed by therapists who are experienced in diagnosing diseases of patients using ultrasonography is by one level or more, and the probability of the occurrence of an error is 20% at maximum. Accordingly, there is a strong demand for a simple and inexpensive method of quantitatively measuring fat content in a target organ using ultrasonography while not being affected by photographing conditions and so on.
In response to such a strong demand, many attempts have been made to measure fat content in a human organ only using ultrasonography. However, it is difficult to quantitatively measure fat content in an organ due to the distortion of image characteristics caused by irregularities in the characteristics of ultrasonograph and photographing conditions.